warning may get a bit geeky.
also not a star wars fan boy so feel free to correct me.
standard european definition, a princess is either a daughter of a hereditary king or queen or married to a prince.
Pocahontas is easy she is the daughter of a chief aka king so no issue.
Mulan was supposedly given some proclamation at the end of the movie but any discussion of why she is a princess may move into areas that may violate board rules.
Princess Leia is not the daughter or a king or queen or married to a prince. but what about Amidala queen of Naboo her mother. well thats an elected position. she was adopted by Queen Breha Organa which brings in a ton of other issues but in standard european royalty an adopted family member did not have hereditary rights to a title.
but I think I have gone too far but I'm assuming everyone has seen the youtube video of leia being introduced to the group
http://www.youtube.com/watch?v=aRMFH71fDIE